Many devices are used in practice as blood glucose meters for self-monitoring by diabetics. In one example, a plurality of reactive test fields is provided on a spoolable test tape in a tape cassette. The reactive test fields are examined photometrically after an application of a small amount of a blood sample to determine the glucose content as exactly and reliably as possible. Such tape cassettes are intended to be inserted as a disposable part into a compact, hand-held device housing to allow the necessary analytical steps to be carried out automatically and rapidly. Unfortunately, many such devices may not be reliable, simple or straightforward to produce via a low-cost design especially suitable for mass production. For the foregoing reasons, additional test devices and systems are needed.